Proper functioning of the elements of the system of discharge and purification of waste water depends to a large extent on their proper engineering. Correct manufacturing and operation of these elements is also essential. The most important parameter for designing is the wastewater volume. The article presents analysis of the sewage amount with the town of Olecko as an example. Analysed was the volumes of wastewater in between 201 and 2014. The largest monthly wastewater volume was recorded in March and the lowest in December. The average amount of generated sewage per 24 h was 2812.3 m³/full day. The amount of sewage varied between 498.0 m³/full day to 6470.0 m³ /full day. The unit wastewater effluent in relation to the number of population was on the average 162.6 per 24h and inhabitant. The work presents also results of a season variability of sewage effluent, selection of the model of auto-regression or matching of an adaptation model.